Scientists testing Lake Michigan for microplastic pollution

Tiny beads can harbor toxic chemicals, bacteria

August 07, 2013|By Abby Olena, Chicago Tribune reporter

Sherri Mason, an associate professor of chemistry with the State University of New York at Fredonia, inspects plastic samples Tuesday in Milwaukee after collecting them in Lake Michigan. (Stacey Wescott, Chicago Tribune)

As the U.S. Brig Niagara sails toward Chicago for the Tall Ships festival, a team of researchers is aboard, sampling the waters of Lake Michigan for pieces of plastic no more than 5 millimeters wide.

Scientists know that these tiny beads, called microplastics, pollute the world's oceans, but the question of microplastic pollution in the Great Lakes is just now beginning to be addressed.

Last summer Sherri Mason, an associate professor of chemistry with the State University of New York at Fredonia, and several collaborators traveled lakes Superior, Huron and Erie, dragging a fine-mesh net behind the Niagara to collect anything floating at the surface.

Their results have yet to be published, but Mason said the nets snagged plenty of microplastics, which has several possible implications for the health of the lakes and people who live nearby.

In oceans, microplastics serve as tiny rafts for microorganisms, including bacteria that could be dangerous to humans. Microplastics also can soak up toxic chemicals. And if fish mistake them for food, it could disrupt food webs by changing their feeding behavior as well as transmitting any chemicals the plastics are carrying.

Potential sources of microplastics include larger pieces of plastic that break down, resin pellets that are used to make things like lawn chairs and plastic bowls, plastic particles used as industrial abrasives and even consumer products like face wash. People might not realize that some exfoliators contain beads made of polyethylene, a type of plastic, Mason said.

This year Mason and the other researchers surveyed Lake Ontario for microplastics; Lake Michigan is the last Great Lake on their list.

Calling the lake "its own separate little beast," Mason said she expects to find high levels of microplastics in Lake Michigan because it borders so many large cities and because water molecules are estimated to swirl around the lake for about 99 years on average before being replaced by water flowing in. Water stays longer only in Lake Superior, according to the National Oceanic and Atmospheric Administration.

On Friday the researchers boarded the Niagara at St. Ignace, Mich., and sailed from Lake Huron into Lake Michigan. After a stop in Milwaukee, the ship is scheduled to arrive in Chicago on Wednesday afternoon. Along the way, researchers planned to collect almost 30 samples.

One scientist who sailed on last summer's research trip is back in her lab, studying the chemicals that may be piggybacking on the microplastics gathered from Superior, Huron and Erie.

The particles "work like a sponge" for pollutants, said Lorena Rios Mendoza, an assistant professor of chemistry at the University of Wisconsin at Superior. One reason is that microplastics have a large surface area in relation to their size, which means there are plenty of places for the chemicals to stick.

In addition, most of the pollutants she's looking for are hydrophobic; they are oily and float on the water rather than dissolving in it, like oil that separates from the other ingredients in salad dressing. Just as those drops of salad oil stick to one another, the pollutants prefer to stick to other hydrophobic things — such as microplastics, which are derived from petroleum.

Rios Mendoza has been looking first at polyaromatic hydrocarbons, long-lived chemical byproducts created by burning fossil fuels. People exposed to high levels of PAHs are at higher risk of developing cancer than others.

In April, Rios Mendoza reported at the American Chemical Society meeting in New Orleans that PAH levels on plastic samples from Lake Erie were double those on plastics gathered from the Atlantic Ocean at the same time.

The Atlantic is obviously much bigger and deeper than Lake Erie, Rios Mendoza said, and it is hard to make clear and accurate comparisons of pollutant levels in two bodies of water that are so different.

Still, she fears that microplastics could be an overlooked source of exposure to dangerous chemicals in the Great Lakes. Rios Mendoza plans next to measure levels of other pollutants on the microplastics the team collected last summer, and she will independently sample Lake Michigan later this month.

Researchers are also concerned about bacteria the microplastics may carry.

"I am sure that there are microbes on those plastic pieces," said Tracy Mincer, an associate scientist at the Woods Hole Oceanographic Institution's department of marine chemistry and geochemistry who co-wrote a recent paper on ocean microplastics.

The study, published online in Environmental Science & Technology in June, found that microplastics act like a space station for microbes, allowing them to thrive in the ocean, where they normally might not, and supporting extensive communities of bacteria and algae, including some potential human pathogens.